The present invention relates to power switches with built-in programmable timers of the type which has its most important commercial application as a control for energizing and de-energizing of electrical appliances used in homes and offices, which emit acoustic or luminous energy, thus simulating the presence of persons, when these are in fact absent. A deterrent effect is thus achieved on intruders, although certain aspects of the invention have a more general application. In such a commercial application, the present invention will form an electric power switch, of the type to be connected in series with a power cord of the appliance and incorporated in the housing of the appliance itself or in its miniaturized version just connected as a mobile switch at the two ends of the power cord carrying the power from the plug to the appliance.
The utilization of mechanical and electromechanical timers for similar purposes is known since long time. These devices have small dimensions and are easily programmed by users without any technical knowledge. Their main drawback lies in the limited amount of on/off sequences which can be programmed during a cycle, which usually covers a time period of a day or a multiple thereof. So it is difficult to have more than 100 on/off sequences per cycle, and the minimum delay between two adjacent sequences is also limited by the precision, with which mechanical markers can be machined and visually seen as distinct. A further drawback of these type of timers lies in their limited lifelength, due to wear of mobile mechanical parts.
Consequently in the last ten years novel fully electronic means of enacting the timer function have been devised, allowing for a very large number of on/off sequences per cycle and remotely controlling a large number of appliances with different of/off sequences for each appliance. In their known form, these devices consist of a central control console, with a built in microprocessor timer and a input keyboard, and of a certain number of peripheral remotely controlled switches, which control energization of the appliances. Unfortunately these devices are not easily programmed by unskilled persons and even the skilled ones need often a well written manual, their installation costs are quite high and they take up a sizable volume.
The object of the present invention is to realize an electric power switch with built-in electronic timer, whose use is straightforward when the user wants it to act as a simulator during his absence, whose dimensions are compatible with the space available in appliances, and having an extremly high number of on/off sequences during any given cycle. Furthermore the lifelength of the electric power switch according to the invention is not limited by wear of mechanical rotating or moving parts and the installation on existing appliances or other electrical apparatus can be handled by any person familiar with electrical power connection practice. A further object of this invention is to provide an electric power switch, which can even compensate for inadvertent oblivion by the user, when leaving without requesting the electric power switch to enter into the simulation mode, which is appropriate during his absence.
To achieve these aims, the electric power switch according to the invention is housed in a container B (FIG. 1), having suitable input and output connections for the power cord and being activated by the user thru manual pression on a suitable knob, toggle or button I, which is well visible for the user. A further smaller commutator S, placed on the side or the underside of the container, having at least a stable position for the "stand-by" mode of operation and another stable position for the "simulation" mode of operation, is operated by the user, when he is either leaving or coming back from a prolonged absence from the room, where the electrical apparatus is installed, which is energized by the electric power switch according to this invention. Thus the operation of this switch is so simple, that even illiterate users can learn and retain its operating procedure. In a refined version of the electric power switch according to the invention, the commutator S has a third intermediate stable position "fail safe stand-by", whereby if the user does not activate the main manual toggle I within a certain period of time since the last manual operation of I, the electric power switch automatically and without any action from the outside goes over to the "simulation" mode and stays in that mode until the manual toggle I is operated again.
In accordance with another feature of the present invention, any dysfunction of the electric power switch which is detected by a special self-check program stored in a suitable memory of the microprocessor gives rise to a coded alarm signal in the form of a characteristic train of very frequent on/off sequences of the power energizing the appliance, thus alerting the user that something is wrong.
Since the use of electronic memories in the timer portion of the electric power switch allows the storing of a very large number of on/off sequences during one cycle, the preferred cycle duration is of one week or a multiple thereof. This has the advantage that the changing pattern of on/off sequences during workdays and weekends is simulated properly when the electric power switch is in the "simulation" mode. In accordance with another feature of the present invention, the microprocessor checks at regular intervals the content of each day section of the stored program of on/off sequences and in case it finds a one day section which is empty (e.g. has not a predetermined minimum amount of on/off sequences), it replaces said one day section with another which is available in the stored program, having a large number of on/off sequences.
This last feature of the invention is particularly useful when installing the electric power switch for the first time, since then, if no particular provisions have been taken, the stored program controlling the timer portion of the electric power switch is completely empty, e.g. all the one day portions of it are empty. After a one day period of use of the electric power switch in the "stand-by" mode, all the empty one-day sections of the stored program will then automatically be filled with the pattern of on/off sequences of the first day, allowing the user to set the electric power switch into the "simulation" mode even though said switch was not in use in the "stand-by" mode for the full length of a recording cycle. Accordingly no special initialization of the timer has to be performed upon the first time of use, which again is very useful and acceptable for technically unskilled users, the only requirement being to use the electric power switch in the "stand-by" mode at least for one day.
Since power failures of short duration (less than 5 minutes) are quite frequent, the critical parts of the timer portion of the electric power switch are protected against loss of power by voltage supplied by a small rechargeable battery or a litium battery, which is provided in the low voltage supply part of the electric power switch. In particular the electronic memory holding the stored program of on/off sequences and the clock are fed by the emergency battery in case of power failure. If the voltage of the emergency battery falls below a certain proper value, the microprocessor, according to another feature of the present invention, detects it and signals it to the user by generating a train of frequent on/off sequences of the power energizing the appliance. This allows the user of either changing the emergency battery or waiting until the battery has been recharged, before setting the electric power switch into the "simulation" mode.
According to another feature of the present invention, in case that the electric power switch has been disconnected from the power outlet for a very long period of time, the appliance it controls not being used or having been inadvertently disconnected by children or other unaware people, the electric power needed to keep the clock and the memory with the stored on/off sequences going is supplied under the day by a photovoltaic cell which charges the emergency battery with the current generated by conversion of daylight, so as to compensate also for the loss of charge of the battery during the night period. A preferred version of such a photovoltaic cell is an amorphous silicon solar cell, which is mounted on the same side of the container B where also the main toggle I is located, so as to get maximum light exposure during the day.
When in the same building more than one electric power switch according to the present invention are installed, it might be useful to control from a central point the setting of said switches into the "simulation" mode or back into the "stand-by" mode. To achieve this and according to another feature of the present invention, the microprocessor is provided with a special decoder circuit, which decodes high frequency signals which are sent along the power lines from a suitable central unit which is operated by the user when leaving or coming back from a prolonged absence. So when a coded high frequency signal is sent along the power lines, each electric power switch goes simultaneously into the "simulation" mode, but each of said switch has a different program of on/off sequences, which simulate e.g. the activity of a person moving from one room to the other. Furthermore and according to another feature of the present invention, the electric power switches are provided with a coded high frequency signal emitting circuit, which sends alarms signal into the power line, in case that the manual toggle I is activated when the electric power switches are operating in the "simulation" mode. Since by definition during the "simulation" mode nobody should be in the building, if there is a charge of the status of any of the toggles I an intruder has penetrated into the building: in this case the coded high frequency signals emitted by the corresponding electric power switch are received and decoded by the central unit, which can then take proper action, e.g. alerting the police over the phone line or energizing an acoustic alarm horn.
In the case where high security is required, the electric power switch is provided according to another feature of the present invention with a voice recognition electronic device, which is speaker dependent and connected to a small microphone, mounted on a suitable face of the container B, so as to be exposed optimally to the mouth of the user, who is entitled to operate it. At the time of first installation of the said switch, the authorized user can teach the voice recognition device by spelling e.g. the works "stand-by" and "simulation" when the commutator S is in the corresponding position and having a special auxiliary button for the "teach" function depressed with his hand. After that, the access to the commutator S is rendered difficult to unauthorized persons, by sealing it e.g. with a lid or any other physical means hampering access and the electric power switch is incorporated into the electrical apparatus which it controls, having only the side with the toggle I and the microphone exposed to the outside. With this particular set-up only the authorized user is able to commute the electric power switch from the "stand-by" into the "simulation" mode and vice versa.
Furthermore it might be useful for the user to have a feed-back, that the electric power switch is properly operating in the "simulation" mode, when the order to do it is either entered by action on the commutator S or by other previously described means. According to another feature of the invention, such an immediate feed-back signal is generated by having after a short delay upon the change of mode a predetermined sequence of few on/off or off/on switches of the power, which end after 10 to 30 seconds, signalling to the user that the microprocessor is working properly. In opposition to this and as already said before, if there is some dysfunction of the electric power switch, the sequences of on/off power switches keep steadily going for as long as the user is taking appropriate action to eliminate said dysfunction.
A further check that the electric power switch according to the present invention is in the "simulation" mode can be achieved by disabling the toggle I in the "simulation" mode, that is either disconnecting from the power the input of the manual switch operated by the toggle I or by suppressing any action that the toggle operated switch might have on the operation of the microprocessor. This feature of the present invention is especially useful in buildings, where security guards performs regular tours, checking the status of electrical apparatus: when operating the toggle I they notice no change in the energized status of the apparatus, they have the proof that the electrical power switch is in the "simulation" mode.
When the appliance or apparatus which is controlled by the electric power switch needs a variable power input according to the user's wishes, it might be useful, according to another feature of the present invention, to incorporate the power regulating means into the electric power switch in such a way, that the microprocessor is storing the on/off sequences and the level of power allowed during the "on" state into said memory during the "stand-by" mode and replays then during the "simulation" mode both the on/off sequences and the level of electric power allowed, as they were stored during the immediately preceding cycle in the "stand-by" mode. The same considerations apply to appliances or apparatus which need for their operation DC voltage supply, in which case the AC/DC converter may be incorporated into the electric power switch, having the added benefit that DC power can be directly supplied to the electronic control timer, if provisions are made in order to have an output of the AC/DC converter with the suitable DC voltage (in most cases 5 V).
The above and other advantages and features of the invention will become apparent upon making reference to the specification to follow, the claims and the drawings.